Sustainable micro-milling of AISI H13 steel: Assessing copaiba oil as an eco-friendly lubricant in MQL-based micro-channel fabrication

The movement toward sustainable manufacturing has heightened the necessity for eco-friendly cutting fluids, which reduce environmental hazards and health risks for machine operators. Although plant-based oils have shown promise as alternatives to traditional mineral-based fluids, their application in precision micro-machining has not been extensively studied. This research investigates, for the first time, the use of copaiba oil – a medicinal plant-based oil known for its anti-inflammatory and antimicrobial properties – as a sustainable cutting fluid in minimum quantity lubrication (MQL)-assisted micro-milling of AISI H13 tool steel. A comparative evaluation is performed against Quimatic synthetic oil and Vascomill vegetable-based oil, with a focus on tribological performance, tool wear, and micro-channel integrity. Using TiAlN-coated carbide micro-endmills (diameter: 400 µm), micro-channels were produced under controlled cutting conditions (cutting speed: 50.26 m/min, feed per tooth: 5 μm, depth of cut: 40 μm). Surface characterization using scanning electron microscopy (SEM) revealed that copaiba oil reduced burr formation while maintaining surface roughness (Ra: 0.05–0.08 μm) comparable to its commercial counterparts, despite higher tool wear. These results provide new insights into the potential of medicinal oils as sustainable lubricants for precision micro-machining. Additionally, the study highlights the potential for incorporating green tribology into micro-manufacturing, addressing both environmental and industrial sustainability. Thus, this research advances environmentally friendly manufacturing solutions, aligning with the aims of green precision engineering.